Programmable irrigation controllers are well-known and are available in a number of different configurations. Historically, programmable irrigation controllers included motor-driven timers that selectively turned on irrigation valves at selected times of the day, on selected days of the week and for selected time durations. The irrigation controllers included a power source at a selected voltage (e.g., 24 volts AC in some systems). The voltage from the power source was first routed to a first selected valve to enable water to flow to sprinklers in a first irrigation area for a first time duration. The voltage from the power source was then routed to a second selected valve to enable water to flow to sprinklers in a second irrigation area for a second time duration. Further valves were subsequently enabled to water additional irrigation areas. The irrigation sequence may have been repeated on a daily basis, may have occurred on certain days of the week, or may have skipped certain days. Setting up the original motor-driven timers was time-consuming and could be challenging for many users.
Over the years, the irrigation controllers with motor-driven timers have been replaced with fully electronic systems with liquid crystal displays (LCDs) and with much greater flexibility in programming the irrigation schedules for multiple irrigation areas. For example, some irrigation areas can be programmed to water on a daily basis, other irrigation areas can be programmed to water on certain days of the week, and other irrigation areas can be programmed to water multiple times in a single day. Regardless of the flexibility of the more recent programmable controllers, many controllers will adhere to the programmed irrigation schedule even while the irrigation areas are being irrigated naturally during a rainfall. It is not unusual to drive by a grassy area during a heavy rainfall and see the sprinklers operating at the same time.
Many conventional sprinkler systems have rain sensor input terminals that can be electrically connected to a rain sensor that collects and accumulates rain. When a sufficient amount of water is accumulated in the sensor, the sensor opens a circuit between the input terminals that causes the programmable controller to discontinue the programmed irrigation schedule until the accumulated rainfall has dissipated (e.g., by evaporation). Such rain sensors may be adequate for many irrigation systems such as, for example, irrigation systems for lawns or other areas where the soil conditions are uniform, the amount of shade is consistent, and the crop (e.g., lawn grass, food crops, or the like) are the same (e.g., require similar amounts of water to thrive). However, many irrigation systems provide water to non-uniform locations. For example, one area may comprise an unshaded lawn, another area may comprise a number of trees, and another area may comprise flower beds. The types of soil in the areas may be different such that one area has a soil that retains moisture and another area needs frequent replenishment of water. Thus, a simple rain sensor may not be adequate to provide sufficient information to an irrigation controller to determine when to provide water to multiple areas with different requirements.
Although remote moisture sensors are available, known remote moisture sensor suffer from deficiencies that reduce the efficacy of such sensors. For example, many known sensors have at least a portion of the sensor located above the surface of the soil being sensed. Thus, such sensors must be protected from damage. Other sensors required solar power to maintain the sensors in an operable state for an extended duration. Other sensors have a limited capability of determining the moisture content of the soil because the sensors only sensed moisture at a single depth or the sensors sense over a broad range of depths without identifying the differing moisture contents at different depths.